1. Field of the Invention
The present invention relates to high security cylinder locks and keys for such locks. More particularly, the present invention relates to cylinder locks that use an additional independent locking mechanism to supplement a conventional pin tumbler locking mechanism.
2. Description of Related Art
Cylinder locks include a cylindrical plug that turns inside a shell. The plug is provided with a key slot and is connected at one end to a mechanism to be operated by the cylinder lock. Inserting the correct key and rotating the plug relative to the shell operates the lock mechanism. Preventing the plug from rotating relative to the shell keeps the mechanism locked.
In a conventional cylinder lock the plug is locked relative to the shell with a pin tumbler mechanism including multiple pins located in a series of evenly spaced pin chambers that extend across the shear surface at the interface between the plug and the shell. Each pin chamber includes at least a lower pin, an upper pin and a spring. Additional pins may also be included in each chamber. The lengths of the pins vary and the upper surface of the correct key is machined to correspond to the lengths of the pins so that the interface between the upper pin and the lower pin in each pin chamber is aligned with the shear surface between the plug and the shell.
With the correct key inserted, the lower pin in each pin chamber is inside the plug and the upper pin in each pin chamber is in the shell. The key can then turn the plug. If the incorrect key is inserted, one or more pins will extend across the shear surface and prevent the plug from being turned.
One application for cylinder locks is in removable core lock mechanisms. In removable core designs the shell must fit into, and be removable from, a standard casing that has an opening that exactly matches the exterior shape of the shell. In one common design, the exterior shape of the shell has a cross section that approximates the shape of the numeral xe2x80x9c8.xe2x80x9d The upper half of the shell provides the required space for the primary pin tumbler mechanism. The lower half is relatively thin-walled and includes an opening to receive the cylindrical plug and locking tab (also called a control sleeve).
To improve security, it is known to add an additional locking mechanism to the cylinder lock that operates independently from, or in conjunction with, the conventional pin tumbler locking mechanism. The additional mechanism includes one or more locking elements that extend across the shear surface between the plug and the shell to prevent the plug from being turned. When the correct key is inserted, the locking elements are allowed to move so that they no longer extend across the shear surface and thereby allow the plug to rotate relative to the shell.
One known type of additional locking mechanism includes a second conventional pin tumbler mechanism. The pins in the second pin tumbler mechanism may contact the side of the key, the bottom of the key or they may be parallel to and adjacent to the first set of pins. Although this solution is effective, it requires additional space in the shell for the additional pin chambers, springs and pins that fit within the chambers. The required additional space in the shell is not always available for conventional cylinder lock designs.
To add a secondary conventional pin tumbler mechanism to a primary pin tumbler locking mechanism is not an option for a removable core design. Therefore, it is highly desirable for any additional locking mechanism between the plug and the shell to be primarily located within the plug, not within the shell.
Nonetheless, it is difficult to fit a supplemental locking mechanism entirely within the plug. The plug must have a key slot that approximately bisects the plug, as well as the pin chambers of the primary locking mechanism. This leaves only limited space within the plug. The space available in the plug is particularly limited in the radial direction, which is the direction needed to accommodate a conventional pin-tumbler design in which a coil spring is axially aligned with a locking pin.
Other known types of supplemental or secondary locking mechanisms are expensive to manufacture or cannot be integrated into existing installed systems in the field.
Yet another problem with conventional cylinder locks relates to the manner in which the key is aligned relative to the locking mechanisms in the lock. In order for the lock to be operated, the key must be inserted and must stop at the correct inserted distance relative to the locking mechanisms inside the cylinder lock.
Conventional cylinder locks do this by providing an alignment stop surface on the end of the key or at the base of the key between the key bow and the key blade. The alignment stop surface at the base or tip of the key contacts a corresponding alignment stop surface at the front or rear of the plug when the key is inserted.
Although putting the stop at the base or tip of the key is standard, it would improve security to put the stop at a non-standard location. This would make copying a key more difficult. A non-standard location for the stop also would make it possible to use keys of different lengths to operate the same lock. It would not be required that the key blade be long enough to reach a stop at the rear of the lock or that the distance from the key bow to the locking elements in the key be fixed.
It is common for a family of similar lock mechanisms to be constructed using five, six or seven conventional pin tumblers. Placing the alignment stop at a non-standard location on the key provides many options for keying, improving security, and varying lock design, particularly when multiple locks of different lengths are used.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a cylinder lock with an additional locking mechanism that fits substantially completely within the plug and supplements a conventional pin tumbler locking mechanism.
A further object of the invention is to provide a cylinder lock that can be used in a removable core design where the locking mechanism does not extend into the upper half of the shell or interfere with the locking tab or other mechanism that locks a removable core cylinder lock into a surrounding shell.
It is still another object of the invention to provide a cylinder lock and key that can be integrated into and be a part of an existing installed door lock system using the original cross sectional shape for the keys and mating keyways.
It is yet another object of the present invention to provide a cylinder lock and key that cooperate to stop the insertion of the key at a desired aligned location relative to the lock without regard to the length of the key.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in art, are achieved in the present invention which is directed to a cylinder lock that includes a shell, a plug having a key slot formed therein, a locking pin movable between a locked position and an unlocked position, a sensor pin movable between an extended position and a retracted position and a flexible coupling connected between the locking pin and the sensor pin.
The plug is rotatably mounted within the shell to define a shear surface between the plug and the shell. The locking pin extends across the shear surface in the locked position to lock the plug against rotation relative to the shell and the sensor pin extends at least partially into the key slot in the extended position. The flexible coupling moves the locking pin to the unlocked position when the sensor pin moves to the retracted position. The coupling is sufficiently flexible that the locking pin can remain in the locked position when the sensor pin moves to the retracted position whenever the locking pin is blocked from moving to the unlocked position.
In the preferred design, the flexible coupling is located entirely inside the plug and the locking pin extends at least partially into the key slot when the locking pin is in the unlocked position. A bias spring is connected to urge the locking pin toward the locked position. The bias spring does not need to be in axial alignment with the locking pin, and it is preferred that the bias spring operate against a flexible rod, forming the flexible portion of the flexible coupling. The rod flexes whenever the sensor pin moves to the retracted position and the locking pin is blocked from moving to the unlocked position. The locking pin may be connected to the flexible rod with an opening in the side of the locking pin.
In the most highly preferred design of the cylinder lock, the flexible coupling includes a cam, the flexible rod and a pivot for the cam to rotate on. The pivot is positioned between the locking pin and the sensor pin and the cam turns on the pivot to move the locking pin to the unlocked position when the sensor pin moves to the retracted position.
The locking pin and sensor pin need not be perpendicular or parallel to the plane of the key blade. It is preferred that they be at an angle between zero and ninety degrees to the plane of the key blade to give them maximum room for the required sliding motion within the radial confines of the plug.
The present invention is also directed to the key for use with the cylinder lock of the invention and to a cylinder lock mechanism including the key and the cylinder lock. The key includes a key bow for turning the key and a key blade having a cross sectional shape selected to fit within the key slot in the plug of the cylinder lock. The key blade includes a locking pin receiving notch at a first location and a contact surface at a second location on the key blade.
The locking pin receiving notch has a size sufficient to receive a locking pin extending into the key slot from the cylinder lock. The locking pin receiving notch cooperates with the locking pin in the cylinder lock and the contact surface cooperates with the sensor pin in the cylinder lock to lock and unlock the plug of the cylinder lock relative to the shell of the cylinder lock. In the most highly preferred embodiment of the invention, the locking pin receiving notch is cut into the key at an angle relative to the plane of the key blade that matches the angle of the locking pin relative to the plane of the key blade.
In another aspect of the key of this invention, the locking pin receiving notch in the key includes an alignment surface contacting the locking pin when the key blade is inserted into the key slot and cooperating with the locking pin to stop insertion of the key blade into the key slot at a desired position relative to the plug of the cylinder lock. This allows the locking pin receiving notch to stop the insertion of the key at the required location for the key to be able to operate the primary pin tumbler locking mechanism.